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Marco Mattavelli and Giorgio Zoia Vector-Tracing Algorithms for Motion Estimation in Large Search Windows
AbstractDespite the several efforts aimed at reducing the complexity, block-based motion estimation remains the most computationally demanding stage of video compression algorithms. This is particularly evident when sequences contain large displacements; very large search windows are needed to achieve high-quality coding when such critical conditions occur. This paper presents a new block-motion-estimation algorithm based on the systematic application of the tracing of motion trajectories on a modified genetic search heuristic. The described technique is able to provide motion estimates in very large search windows with optimal coding results. The complexity-reduction factor ranges up to more than two orders of magnitude. The technique can be applied to any macroblock-based video compression standard and to any group of picture structure.
RAR  268
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Ertem Tuncel, and Levent Onural Utilization of the Recursive Shortest Spanning Tree Algorithm for Video-Object Segmentation by 2-D Affine Motion Modeling
AbstractA novel video-object segmentation algorithm is proposed, which takes the previously estimated 2-D dense motion vector field as input and uses the generalized recursive shortest spanning tree method to approximate each component of the motion vector field as a piecewise planar function. The algorithm is successful in capturing 3-D planar objects in the scene correctly, with acceptable accuracy at the boundaries. The proposed algorithm is fast and requires no initial guess about the segmentation mask. Moreover, it is a hierarchical scheme which gives finest to coarsest segmentation results. The only external parameter needed by the algorithm is the number of segmented regions that essentially control the level at which the coarseness the algorithm would stop. The proposed algorithm improves the analysis model developed in the European COST211 framework.
RAR  467
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Kevin Hilman, Hyun Wook Park, and Yongmin Kim,Fellow, EEE Using Motion-Compensated Frame-Rate Conversion for the Correction of 3 : 2 Pulldown Artifacts in Video Sequences

RAR  283
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Theophilos Papadimitriou, Konstantinos I. Diamantaras, Michael G. Strintzis, and Manos Roumeliotis Robust Estimation of Rigid-Body 3-D Motion Parameters Based on Point Correspondences
AbstractCurrently, the most popular method of converting 24 frames per second (fps) film to 60 fields/s video is to repeat each odd-numbered frame for 3 fields and each even-numbered frame for 2 fields. This method is known as 3 : 2 pulldown and is an easy and inexpensive way to perform 24 fps to 60 fields/s frame-rate conversion. However, the 3 : 2 pulldown introduces artifacts, which are especially visible when viewing on progressive displays and during slow-motion playback. We have developed a motion-compensated frame-rate conversion algorithm to reduce the 3 : 2 pulldown artifacts. By using frame-rate conversion with interpolation instead of field repetition, mean square error and blocking artifacts are reduced significantly. The techniques developed here can also be applied to the general frame-rate conversion problem.
RAR  300
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Dimitrios Tzovaras, Nikiforos Ploskas, and Michael G. Strintzis Rigid 3-D Motion Estimation Using Neural Networks and Initially Estimated 2-D Motion Data
AbstractThis paper extends a known efficient technique for rigid threedimensional (3-D) motion estimation so as to make it applicable to motion-estimation problems occuring in image sequence coding applications. The known technique estimates 3-D motion using previously evaluated 3-D correspondence. However, in image sequence coding applications, 3-D correspondence is unknown and usually only two-dimensional (2-D) motion vectors are initially available. The novel neural network (NN) introduced in this paper uses initially estimated 2-D motion vectors to estimate 3-D rigid motion, and is therefore suitable for image sequence coding applications. Moreover, it is shown that the NN introduced in this paper performs extremely well even in cases where 3-D correspondence is known with accuracy. Experimental results are presented for the evaluation of the proposed scheme.
RAR  305
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Renxiang Li, Bing Zeng, and Ming L. Liou Reliable Motion Detection/Compensation for Interlaced Sequences and Its Applications to Deinterlacing
AbstractIn this letter, we present a new method for the motion detection/compensation between opposite parity fields in interlaced video sequences. We introduce a phase-correction filter, which is applied to one type (even or odd) of fields before motion detection/compensation. By means of this phase-correction filter, the motion-compensated PSNR has been improved by more than 2 dB, on average. We also present a new deinterlacing algorithm based on the newly developed motion detection/compensation. This algorithm requires storing one field only, and the phase-corrected field is used for both motion detection/compensation and intrafield deinterlacing, thus making the proposed algorithm computationally very efficient. Excellent deinterlacing results have been obtained.
RAR  176
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Yap-Peng Tan, Drew D. Saur, Sanjeev R. Kulkarni, and Peter J. Ramadge, Fellow Rapid Estimation of Camera Motion from Compressed Video with Application to Video Annotation
AbstractAs digital video becomes more pervasive, efficient ways of searching and annotating video according to content will be increasingly important. Such tasks arise, for example, in the management of digital video libraries for content-based retrieval and browsing. In this paper, we develop tools based on camera motion for analyzing and annotating a class of structured video using the low-level information available directly from MPEG-compressed video. In particular, we show that in certain structured settings, it is possible to obtain reliable estimates of camera motion by directly processing data easily obtained from the MPEG format. Working directly with the compressed video greatly reduces the processing time and enhances storage efficiency. As an illustration of this idea, we have developed a simple basketball annotation system which combines the low-level information extracted from an MPEG stream with the prior knowledge of basketball structure to provide high-level content analysis, annotation, and browsing for events such as wide-angle and close-up views, fast breaks, probable shots at the basket, etc. The methods used in this example should also be useful in the analysis of high-level content of structured video in other domains.
RAR  385
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Injong Rhee, Graham R. Martin, S. Muthukrishnan, and Roger A. Packwood Quadtree-Structured Variable-Size Block-Matching Motion Estimation with Minimal Error
AbstractThis paper reports two efficient quadtree-based algorithms for variable-size block matching (VSBM) motion estimation. The schemes allow the dimensions of blocks to adapt to local activity within the image, and the total number of blocks in any frame can be varied while still accurately representing true motion. This permits adaptive bit allocation between the representation of displacement and residual data, and also the variation of the overall bit-rate on a frame-by-frame basis. The first algorithm computes the optimal selection of variable-sized blocks to provide the best-achievable prediction error under the fixed number of blocks for a quadtree-based VSBM technique. The algorithm employs an efficient dynamic programming technique utilizing the special structure of a quadtree. Although this algorithm is computationally intensive, it does provide a yardstick by which the performance of other more practical VSBM techniques can be measured. The second algorithm adopts a heuristic way to select variable- sized square blocks. It relies more on local motion information than on global error optimization. Experiments suggest that the effective use of local information contributes to minimizing the overall error. The result is a more computationally efficient VSBM technique than the optimal algorithm, but with a comparable prediction error.
RAR  165
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Chung J. Kuo, Chia H. Yeh, and Souheil F. Odeh Polynomial Search Algorithms for Motion Estimation
AbstractThis paper proposes a polynomial search (PS) algorithm and architecture to solve the motion-estimation problem in video coding. Simulation results show that the proposed method is not only flexible, but also requires fewer computations to achieve the same mean absolute error results (for QCIF and sub-QCIF video) compared with the existing fast-search algorithms. Finally, a VLSI architecture is also developed to efficiently implement the PS algorithm.
RAR  125
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Prakash Ishwar and Pierre Moulin On Spatial Adaptation of Motion-Field Smoothness in Video Coding
AbstractMost motion-compensation methods dealt with in the literature make strong assumptions about the smoothness of the underlying motion field. For instance, block-matching algorithms assume a blockwise-constant motion field and are adequate for translational motion models; control-grid interpolation assumes a blockwise bilinear motion field and captures zooming and warping fairly well. Time-varying imagery, however, often contains both types of motion (as well as others), and hence exhibits a high degree of spatial variability of its motion-field smoothness properties. We develop a simple method to spatially adapt the smoothness of the motion field. The proposed method demonstrates substantial improvements in video quality over a wide range of bit rates. To this end, we introduce the notion of a motion field that is characterized by a set of labels. The labels provide the flexibility to adaptively switch between two different motion models locally. The individual motion models have very different smoothness properties. The switched framework for motion compensation performs significantly better than each of its constituent motion models, in terms of both visual quality and signal-to-noise ratio (0.30.7 dB on the average). Finally, we develop an extension of this method that enhances the overlapped block motion compensation scheme by allowing spatial adaptation of the window function.
RAR  598
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Chok-Kwan Cheung and Lai-Man Po Normalized Partial Distortion Search Algorithm for Block Motion Estimation
AbstractMany fast block-matching algorithms reduce computations by limiting the number of checking points. They can achieve high computation reduction, but often result in relatively higher matching error compared with the full-search algorithm. In this letter, a novel fast block-matching algorithm named normalized partial distortion search is proposed. The proposed algorithm reduces computations by using a halfway-stop technique in the calculation of block distortion measure. In order to increase the probability of early rejection of non-possible candidate motion vectors, the proposed algorithm normalized the accumulated partial distortion and the current minimum distortion before comparison. Experimental results show that the proposed algorithm can maintain its mean square error performance very close to the full search algorithm while achieving an average computation reduction of 1213 times, with respect to the full-search algorithm.
RAR  123
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Xudong Song, Tihao Chiang, Xiaobing Lee, and Ya-Qin Zhang, Fellow New Fast Binary Pyramid Motion Estimation for MPEG2 and HDTV Encoding
AbstractA novel Fast Binary Pyramid Motion Estimation (FBPME) algorithm is presented in this paper. The proposed FBPME scheme is based on binary multiresolution layers, exclusive- or (XOR) Boolean block matching, and a -scale tiling search scheme. Each video frame is converted into a pyramid structure of 1 binary layers with resolution decimation, plus one integer layer at the lowest resolution. At the lowest resolution layer, the -scale tiling search is performed to select initial motion vector candidates. Motion vector fields are gradually refined with the XOR Boolean block-matching criterion and the -scale tiling search schemes in higher binary layers. FBPME performs several thousands times faster than the conventional full-search block-matching scheme at the same PSNR performance and visual quality. It also dramatically reduces the bus bandwidth and on-chip memory requirement. Moreover, hardware complexity is low due to its binary nature. Fully functional software MPEG-2 MP@ML encoders and Advanced Television Standard Committee High Definition Television encoders based on the FBPME algorithm have been implemented. FBPME Hardware architecture has been developed and is being incorporated into single-chip MPEG encoders. A wide range of video sequences at various resolutions has been tested. The proposed algorithm is also applicable to other digital video compression standards such as H.261, H.263, and MPEG4.
RAR  563
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Jorge Sastre, Antonio Ferreras, and Jos Flix Hernndez-Gil Motion Vector Size-Compensation Based Method for Very Low Bit-Rate Video Coding
AbstractIn this paper, a new method to achieve better compression efficiency in low bit-rate video coding is proposed. It is based on a global bit-rate reduction at a macroblock level, optimizing the number of bits to code each macroblock as a whole by means of motion vector and headers size compensation. The selection of the best motion vector and different coding modes for each block of the current picture will be made depending not only on trying to choose the best prediction for the block, but also on the number of bits to code the associate headers, introducing some kind of penalization in the cost function. This method improves efficiency on video compression for all qualities, but especially for low-quality video coding, whose efficiency improvement can reach 17%. Its implementation is simple, and compatible with most video-compression standards (H.263, MPEG, etc.). Results of the algorithm in a state-of-the-art H.263+ codec are presented, and demonstrate that the efficiency enhancement is achieved with minimal time-processing increase, and even decrease, in some conditions.
RAR  440
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Oscal T.-C. Chen Motion Estimation Using a One-Dimensional Gradient Descent Search
AbstractThis work presents a low-complexity high-performance motion estimation method using a one-dimensional (1-D) gradient descent search. The proposed method consists of initial-point determination, initial-direction determination, a gradient descent search using variable step sizes and conjugate directions, and convergence checking. For each block, one of the original and predictive points with the best block-matching performance is the initial point where the predictive ones are motion vectors of its neighboring four searched blocks. In addition, the searching path is optimized by determining the initial direction based on the vector from the original point to the initial point. After determining the initial point and direction, the gradient descent search using variable step sizes and conjugate directions is performed until the searched point attains a better performance than its neighboring points. Moreover, variable step sizes for moving and slowly moving, or stationary blocks, are well addressed to improve the convergence performance of a gradient descent search. Simulation results demonstrate that our method yields a superior performance in terms of computational complexity and picture quality as compared to the three-step search, 1-D full search, block-based gradient descent search, and one-at-a-time search methods.
RAR  239
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Peter Eisert, Thomas Wiegand, and Bernd Girod, Fellow Model-Aided Coding: A New Approach to Incorporate Facial Animation into Motion-Compensated Video Coding

RAR  696
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Zhong-Li He, Chi-Ying Tsui, Kai-Keung Chan, and Ming L. Liou, Fellow Low-Power VLSI Design for Motion Estimation Using Adaptive Pixel Truncation
AbstractWe show that traditional waveform coding and 3-D model-based coding are not competing alternatives, but should be combined to support and complement each other. Both approaches are combined such that the generality of waveform coding and the efficiency of 3-D model-based coding are available where needed. The combination is achieved by providing the block-based video coder with a second reference frame for prediction, which is synthesized by the model-based coder. The model-based coder uses a parameterized 3-D head model, specifying shape and color of a person. We therefore restrict our investigations to typical videotelephony scenarios that show head-and-shoulder scenes. Motion and deformation of the 3-D head model constitute facial expressions which are represented by facial animation parameters (FAPs) based on the MPEG-4 standard. An intensity gradient-based approach that exploits the 3-D model information is used to estimate the FAPs, as well as illumination parameters, that describe changes of the brightness in the scene. Model failures and objects that are not known at the decoder are handled by standard block-based motion-compensated prediction, which is not restricted to a special scene content, but results in lower coding efficiency. A Lagrangian approach is employed to determine the most efficient prediction for each block from either the synthesized model frame or the previous decoded frame. Experiments on five video sequences show that bit-rate savings of about 35% are achieved at equal average peak signal-to-noise ratio (PSNR) when comparing the model-aided codec to TMN-10, the state-of-the-art test model of the H.263 standard. This corresponds to a gain of 23 dB in PSNR when encoding at the same average bit rate. semantic content of the frames and can therefore be used for arbitrary scenes.
RAR  215
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Yan Yang and Sheila S. Hemami Generalized Rate-Distortion Optimization for Motion-Compensated Video Coders
AbstractThis paper addresses jointly rate-distortion optimal selection of coding parameters in a general motion-compensated video coder. The general coder uses variable-block-size motion estimation and multimode residual coding. This is essentially the optimal bit-allocation problem for an individual frame at a given rate constraint. This paper not only gives the general formulation and solution using the Lagrange multiplier method and dynamic programming, but also demonstrates howthe general theory can be adapted and applied to both an MPEG-like coder and a motion-compensated wavelet coder. Simulations demonstrate that both proposed coders outperform MPEG (TM5) by 0.71.3 dB at a variety of bit rates, with the gain provided by both better motion estimation and the joint-parameter optimization. The technique is applicable to MPEG-compliant coders with fixed block-size motion estimation and provides a gain of 0.50.7 dB over TM5. The optimization approach can also be applied to distortion-constrained coding, and therefore allows a fine tuning of either the rate or distortion to follow any desired profile.
RAR  491
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Luis Salgado, Narciso Garca, Jos M. Menndez, and Enrique Rendn Efficient Image Segmentation for Region-Based Motion Estimation and Compensation
AbstractAn intra-frame segmentation strategy to assist region- based motion estimation and compensation is presented. It is based on the multiresolution application of a histogram clustering and a probabilistic relaxation-labeling algorithm, followed by a local gradient-based bottom-up merging procedure. Specially suited for region-based video coding, it strongly differs from other proposals in that it generates arbitrary shaped image regions with pixel accuracy at a low computational cost, while allowing full reconstruction of the segmentation at the decoder without the transmission of any region description information.
RAR  484
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Yankang Wang, Yanqun Wang, and Hideo Kuroda A Globally Adaptive Pixel-Decimation Algorithm for Block-Motion Estimation
AbstractFor the estimation of block-motion vectors, common techniques use uniform pixel-decimation patterns to select pixels to evaluate block-matching criterion, while more recent techniques use adaptive pixel patterns and have achieved better efficiency. However, these adaptive techniques still require an initial division of a block into a set of uniform regions, and therefore, are locally adaptive in essence. Our proposed scheme, which does not fix any regions at the beginning and selects pixels only when they have the features important in determining a match, shows an improvement in performance over the existing adaptive schemes. Our results suggest the usefulness of this method in block-motion estimation for low-bit-rate video coding, particularly in video phone and video conferencing.
RAR  205
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Jong-Nam Kim and Tae-Sun Choi A Fast Full-Search Motion-Estimation Algorithm Using Representative Pixels and Adaptive Matching Scan
AbstractThe ability to construct intracoded frame from motion-compensated intercoded frames directly in the compressed domain is important for efficient video manipulation and composition. In the context of motion-compensated discrete cosine transform (DCT)-based coding of video as in MPEG video, this problem of DCT-domain inverse motion compensation has been studied and, subsequently, improved faster algorithms were proposed. These schemes, however, treat each 8 8 block as a fundamental unit, and do not take into account the fact that in MPEG, a macroblock consists of several such blocks. In this paper, we show how shared information within a macroblock, such as a motion vector and common blocks, can be exploited to yield substantial speedup in computation. Compared to previous brute-force approaches, our algorithms yield about 44% improvement. Our technique is independent of the underlying computational or processor model, and thus can be implemented on top of any optimized solution. We demonstrate an improvement by about 19%, and 13.5% in the worst case, on top of the optimized solutions presented in existing literature. preserve the quality of video. The computational efficiency also leads to higher throughput in dealing with the enormous data rates in a network environment. Techniques for the conversion of MC-DCT intercoded frames into DCT intracoded frames also form the basis for fast extraction of specially reduced images in MPEG-1 [6] and MPEG-2 video [7]. This problem of DCT-domain inverse motion compensation, i.e., the conversion of intercoded frames into intracoded frames directly in the DCT domain without the need for full decompression for MPEG video was studied in Chang and Messerschmitt [1], and subsequently in [2], [3]. The idea of the algorithm in [1] is to represent a target block as a summation of horizontally and/or vertically displaced anchor blocks. Then, the DCT values of the target block is constructed using the precomputed DCT values of the shifting matrices. The general setup is shown in
RAR  165
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Junehwa Song and Boon-Lock Yeo A Fast Algorithm for DCT-Domain Inverse Motion Compensation Based on Shared Information in a Macroblock
AbstractA full-search based block-matching algorithm for motion estimation has a major problem of significant computational load. To solve this problem, extensive research in fast-motion estimation algorithms have been carried out. However, most of them have some degradation in the predicted image from the reduced computation. To decrease the amount of significant computation of the full-search algorithm, we propose a fast block-matching algorithm based on an adaptive matching scan and representative pixels without any degradation of the predicted image. By using Taylor series expansion, we obtain the representative pixels and show that the block-matching errors from the reference block and candidate blocks are proportional to the block complexity. With the derived result, we propose a fast full-search algorithm with adaptive scan direction in block matching. Experimentally, our proposed algorithm is very efficient in terms of computational speedup, and is the fastest among all the conventional full-search algorithms. Therefore, our algorithm is useful in VLSI implementation of video encoders for real-time encoding.
RAR  285
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Vassilios Christopoulos and Jan Cornelis A Center-Biased Adaptive Search Algorithm for Block Motion Estimation
AbstractA number of sub-optimal, but faster, search algorithms have been proposed in the literature, in order to alleviate the complexity associated with motion estimation by the full-search method. A new sub-optimal center-biased adaptive search algorithm for motion estimation is proposed; we refer to this algorithm as center-biased dynamic MInima Bounded Area Search (MIBAS) algorithm. The novelty of MIBAS is the checking point pattern at each subsequent step, composed of points lying in the area bounded by two local minima found at the present step, rather than points lying in a small neighborhood around a local minimum. The simulation results show that, compared to other fast algorithms, the center-biased MIBAS is more robust and produces smaller prediction errors and more reliable motion vectors, while it has a comparable computational complexity.
RAR  114
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Jer Min Jou, Pei-Yin Chen, and Jian-Ming Sun The Gray Prediction Search Algorithm for Block Motion Estimation
AbstractDue to the temporal and spatial correlation of the image sequence, the motion vector of a block is highly related to the motion vectors of its adjacent blocks in the same image frame. If we can obtain useful and enough information from the adjacent motion vectors, the total number of search points used to find the motion vector of the block may be reduced significantly. Using that idea, an efficient gray prediction search (GPS) algorithm for block motion estimation is proposed in this paper. Based on the gray system theory, the GPS can determine the motion vectors of image blocks quickly and correctly. The experimental results show that the proposed algorithm performs better than other search algorithms, such as 3SS, CS, PHODS, 4SS, BBGDS, SES, and PSA, in terms of six different measures: 1) average mean square error per pixel; 2) average peak signal-to-noise ratio; 3) average prediction errors per pixel; 4) average entropy of prediction errors; 5) average percentage of unpredictable pels per frame; and 6) average search points per block.
RAR  268
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Jungwoo Lee, and Bradley W. Dickinson, Fellow Subband Video Coding with Scene-Adaptive Hierarchical Motion Estimation
Abstract This paper presents a new motion-compensated subband video-coding technique using variable reference-frame positions for motion estimation. The work builds on temporal segmentation for determining the reference-frame positions and incorporates multiresolution motion estimation in the subband domain. The key advantage of the new algorithm is the complexity reduction in motion estimation that uses the multiresolution property of subband decomposition. Temporal segmentation is performed with the lowest spatial subband, based on the detection of two types of scene change. The frames of input video are split into seven spatial subbands, and the motion vectors for each subband are generated by a hierarchical motion-estimation algorithm. Blockwise differential pulse code modulation (DPCM) and a uniform quantizer are used for the lowest subband of the first frame only, and the subbands of all other cases are coded by PCM with a dead-zone quantizer. Simulation results show that our scene-adaptive scheme compares favorably with a fixed interpolation structure.
RAR  300
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Aljoscha Smolic, Bela Makai, and Thomas Sikora Real-Time Estimation of Long-Term 3-D Motion Parameters for SNHC Face Animation and Model-Based Coding Applications
AbstractIn this paper, we present two recursive methods for the real-time estimation of long-term three-dimensional (3-D) motion parameters from monocular image sequences suitable for synthetic/natural hybrid coding face animation and model-based coding applications. Based on feature point extractions in every frame, the 3-D motion parameters of a human face are estimated with a predictive approach. The first method uses a recursive linear least squares approach and the second employs a nonlinear extended Kalman filter, which does not rely on a linearized model of the face motion. Both methods perform a prediction and correction loop at every time step. Compared to other methods described in the literature, the recursive and predictive structure of the proposed estimation process solves the problem of error accumulation in long-term motion estimation. This makes the estimation stable and consistent over long periods. Experimental results are presented for synthetic data and real image sequences, which demonstrate the performance of the estimation methods and compare the two approaches.
RAR  414
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Christian J. van den Branden Lambrecht, Daniele M. Costantini, Giovanni L. Sicuranza, and Murat Kunt, Fellow Quality Assessment of Motion Rendition in Video Coding
AbstractThis paper addresses the issue of test and quality assessment of motion rendition in digital video coding. Motion estimation and compensation are critical modules in video coders, as they are the most demanding resources and largely account for the visual quality of the resulting compressed stream. The testing of such modules is thus very important. A computational metric, based on a spatiotemporal model of the human visual system and of human motion sensing, is proposed and used to evaluate MPEG-2 compressed video. The metric is able to assess the quality of motion rendition and exhibits a good correlation with subjective data.
RAR  355
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Jiajun Zhang, M. Omair Ahmad, and M. N. S. Swamy, Fellow Quadtree Structured Region-Wise Motion Compensation for Video Compression
Abstract The conventional variable-size block motioncompensation technique, even though superior to the fixed-size block motion-compensation technique, cannot fully utilize the motion information of a frame for its partitioning. This paper presents a quadtree structured region-wise motion-compensation technique that utilizes more effectively the motion content of a frame in terms of the shape, size, and location of the partitioned regions. The proposed technique is based on a new coding scheme of the quadtree structure, where a two-bit code is used. The partitioning of a given frame is carried out through the processes of merging and combining. The merging process partitions the frame into a number of regions by carrying out all possible 4-to-1, 3-to-1, and 2-to-1 merges along the quadtree hierarchy according to some specified criteria, while the combining process combines some of the partitioned regions that have the same motion vector into a single region. The motion vectors of the resulting partitioned regions are coded by a new coding scheme that uses the temporal correlation of the motion fields. Test results of applying the proposed method on a number of MPEG video sequences are included. These results indicate that the proposed method can provide a significantly improved rate-distortion performance.
RAR  507
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Fang-Hsuan Cheng and San-Nan Sun New Fast and Efficient Two-Step Search Algorithm for Block Motion Estimation
AbstractBlock motion estimation using full search is computationally intensive. Previously proposed fast algorithms reduce the computation by limiting the number of searching locations. This is accomplished at the expense of less accuracy of motion estimation and gives rise to an appreciably higher mean squared error (MSE) for motion-compensated images. In this paper, we present a new fast and efficient search algorithm for block motion estimation that produces better quality performance and less computational time compared with a three-step search (TSS) algorithm. The proposed algorithms are based on the ideas of dithering pattern for pixel decimation, multiple-candidate for pixel-decimation-based full search, and center-based distribution of motion vector. From the experimental results, the proposed algorithm is superior to TSS in both quality performance (about 0.2 dB) and computational complexity (about half). Kunt et al. [8], Rao and Yip [9], and Dufaux and Moscheni [10]. These algorithms had been developed for very different applications such as image sequence analysis, machine vision, robotics, image sequence restoration, and video sequence coding.
RAR  179
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Peter H. W. Wong and Oscar C. Au Modified One-Bit Transform for Motion Estimation
AbstractMotion estimation using the one-bit transform (1BT) was proposed in [1] to achieve large computation reduction. However, it degrades the predicted image by almost 1 dB as compared with full search. In this paper, we propose a modification to the 1BT by adding conditional local searches. Simulation results show that the proposed modification improves the peak signal-to-noise ratio (PSNR) significantly at the expense of slightly increased computational complexity. A variant of the proposed modification called M2SSFS is found to be particularly good for high quality, high bit rate video coding. In the MPEG-1 simulation, its PSNR is within 0.1 dB from that of full search at bit rates higher than
RAR  132
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Thomas Wiegand, Xiaozheng Zhang, and Bernd Girod, Fellow Long-Term Memory Motion-Compensated Prediction
AbstractLong-term memory motion-compensated prediction extends the spatial displacement vector utilized in block-based hybrid video coding by a variable time delay permitting the use of more frames than the previously decoded one for motioncompensated prediction. The long-term memory covers several seconds of decoded frames at the encoder and decoder. The use of multiple frames for motion compensation in most cases provides significantly improved prediction gain. The variable time delay has to be transmitted as side information requiring an additional bit rate which may be prohibitive when the size of the long-term memory becomes too large. Therefore, we control the bit rate of the motion information by employing rateconstrained motion estimation. Simulation results are obtained by integrating long-term memory prediction into an H.263 codec. Reconstruction PSNR improvements up to 2 dB for the Foreman sequence and 1.5 dB for the MotherDaughter sequence are demonstrated in comparison to the TMN-2.0 H.263 coder. The PSNR improvements correspond to bit-rate savings up to 34 and 30%, respectively. Mathematical inequalities are used to speed up motion estimation while achieving full prediction gain.
RAR  339
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Aljoscha Smolic, Thomas Sikora, and Jens-Rainer Ohm Long-Term Global Motion Estimation and Its Application for Sprite Coding, Content Description, and Segmentation
AbstractIn this paper, we present a new technique for longterm global motion estimation of image objects. The estimated motion parameters describe the continuous and time-consistent motion over the whole sequence relatively to a fixed reference coordinate system. The proposed method is suitable for the estimation of affine motion parameters as well as for higher order motion models like the parabolic modelcombining the advantages of feature matching and optical flow techniques. A hierarchical strategy is applied for the estimation, first translation, affine motion, and finally higher order motion parameters, which is robust and computationally efficient. A closed-loop prediction scheme is applied to avoid the problem of error accumulation in long-term motion estimation. The presented results indicate that the proposed technique is a very accurate and robust approach for long-term global motion estimation, which can be used for applications such as MPEG-4 sprite coding or MPEG-7 motion description. We also show that the efficiency of global motion estimation can be significantly increased if a higher order motion model is applied, and we present a new sprite coding scheme for on-line applications. We further demonstrate that the proposed estimator serves as a powerful tool for segmentation of video sequences.
RAR  2109
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Gagan B. Rath and Anamitra Makur Iterative Least Squares and Compression Based Estimations for a Four-Parameter Linear Global Motion Model and Global Motion Compensation
AbstractIn this paper, a four-parameter model for global motion in image sequences is proposed. The model is generalized and can accommodate global object motions besides the motions due to the camera movements. Only the PAN and the ZOOM global motions are considered because of their relatively more frequent occurrences in real video sequences. Besides the traditional leastsquares estimation scheme, two more estimation schemes based on the minimization of the motion field bit rate and the global prediction error energy are proposed. Among the three estimation schemes, the iterative least-squares estimation is observed to be the best because of the least computational complexity, accuracy of the estimated parameters, and similar performance as with the other schemes. Four global motion compensation schemes including the existing pixel-based forward compensation are proposed. It is observed that backward compensation schemes perform similarly to the corresponding forward schemes except for having one frame delay degradation. The pixel-based forward compensation is observed to have the best performance. A new motion vector coding scheme is proposed which has similar performance as the two-dimensional entropy coding but needs much less computation. Using the proposed coding scheme with the pixel-based forward compensation, we obtain 61.85% savings in motion field bit rate over the conventional motion compensation for the Tennis sequence.
RAR  461
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Yankang Wang and Hideo Kuroda Hilbert Scanning Search Algorithm for Motion Estimation
Abstract Block-matching algorithms, such as TSS and DSWA/IS, are widely used for motion estimation in low-bit-rate video coding. The assumption behind these algorithms is that when the matching block moves away from the optimal block, the difference between them increases monotonically. Unfortunately, this assumption is often invalid, and therefore leads to a high possibility for the result to be trapped to local minima. In this research, we proposed a new multiple-candidate search scheme, Hilbert scanning search algorithm (HSSA), in which the assumption of global monotonicity is not necessary and the local monotonicity can be effectively explored with binary search around each candidate. In HSSA, the number of initial candidates and a threshold to control the selection of candidates from one stage to the next can be adjusted to meet the required search accuracy and/or speed. With properly chosen parameters, the HSSA converges to their optimal results faster and with better accuracy than the conventional block-matching algorithms.
RAR  245
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Wolfgang Niehsen and Michael Brunig Covariance Analysis of Motion-Compensated Frame Differences
AbstractThe second-order statistics of motion-compensated frame differences in a low-bit-rate hybrid video coding scheme with overlapped block motion compensation are investigated. Based on the empirical covariance sequence, an adequate compound covariance model is developed. The prediction gain for motion-compensated frame differences is evaluated, and the performance of the discrete cosine transform for interframe transform coding is discussed.
RAR  96
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Jie Wei and Ze-Nian Li An Efficient Two-Pass MAP-MRF Algorithm for Motion Estimation Based on Mean Field Theory
AbstractThis paper presents a two-pass algorithm for estimating motion vectors from image sequences. In the proposed algorithm, the motion estimation is formulated as a problem of obtaining the maximum a posteriori in the Markov random field (MAP-MRF). An optimization method based on the mean field theory (MFT) is opted to conduct the MAP search. The estimation of motion vectors is modeled by only two MRFs, namely, the motion vector field and unpredictable field. Instead of utilizing the line field, a truncation function is introduced to handle the discontinuity between the motion vectors on neighboring sites. In this algorithm, a double threshold preprocessing pass is first employed to partition the sites into three regions, whereby the ensuing MFT-based pass for each MRF is conducted on one or two of the three regions. With this algorithm, no significant difference exists between the block-based and pixel-based MAP searches any more. Consequently, a good compromise between precision and efficiency can be struck with ease. To render our algorithm more resilient against noises, the mean absolute difference instead of mean square error is selected as the measure of difference, which is more reliable according to the knowledge of robust statistics. This is supported by our experimental results from both synthetic and real-world image sequences. The proposed two-pass algorithm is much faster than any other MAP-MRF motion estimation method reported in the literature so far.
RAR  585
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Bo Shen, Ishwar K. Sethi, and Bhaskaran Vasudev Adaptive Motion-Vector Resampling for Compressed Video Downscaling
AbstractDigital video is becoming widely available in compressed form, such as a motion JPEG or MPEG coded bitstream. In applications such as video browsing or picture-in-picture, or in transcoding for a lower bit rate, there is a need to downscale the video prior to its transmission. In such instances, the conventional approach to generating a downscaled video bitstream at the video server would be to first decompress the video, perform the downscaling operation in the pixel domain, and then recompress it as, say, an MPEG bitstream for efficient delivery. This process is computationally expensive due to the motion-estimation process needed during the recompression phase. We propose an alternative compressed domain-based approach that computes motion vectors for the downscaled (N= 2.N= 2) video sequence directly from the original motion vectors for the N . N video sequence. We further discover that the scheme produces better results by weighting the original motion vectors adaptively. The proposed approach can lead to significant computational savings compared to the conventional spatial (pixel) domain approach.
RAR  318
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Jie-Bin Xu, Lai-Man Po, and Chok-Kwan Cheung Adaptive Motion Tracking Block Matching Algorithms for Video Coding
AbstractIn most block-based video coding systems, the fast block matching algorithms (BMAs) use the origin as the initial search center, which may not track the motion very well. To improve the accuracy of the fast BMAs, a new adaptive motion tracking search algorithm is proposed in this paper. Based on the spatial correlation of motion blocks, a predicted starting search point, which reflects the motion trend of the current block, is adaptively chosen. This predicted search center is found closer to the global minimum, and thus the center-biased BMAs can be used to find the motion vector more efficiently. Experimental results show that the proposed algorithm enhances the accuracy of the fast center-biased BMAs, such as the new three-step search, the four-step search, and the block-based gradient descent search, as well as reduces their computational requirement.
RAR  183
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Patrick Bouthemy, Marc Gelgon, and Fabrice Ganansia A Unified Approach to Shot Change Detection and Camera Motion Characterization
AbstractThis paper describes an original approach to partitioning of a video document into shots. Instead of an interframe similarity measure which is directly intensity based, we exploit image motion information, which is generally more intrinsic to the video structure itself. The proposed scheme aims at detecting all types of transitions between shots using a single technique and the same parameter set, rather than a set of dedicated methods. The proposed shot change detection method is related to the computation, at each time instant, of the dominant image motion represented by a two-dimensional affine model. More precisely, we analyze the temporal evolution of the size of the support associated to the estimated dominant motion. Besides, the computation of the global motion model supplies by-products, such as qualitative camera motion description, which we describe in this paper, and other possible extensions, such as mosaicing and mobile zone detection. Results on videos of various content types are reported and validate the proposed approach.
RAR  2098
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John C.-H. Ju, Yen-Kuang Chen, and S. Y. Kung A Fast Rate-Optimized Motion Estimation Algorithm for Low-Bit-Rate Video Coding
AbstractMotion estimation is known to be the main bottleneck in real-time encoding applications, and the search for an effective motion estimation algorithm (in terms of computational complexity and compression efficiency) has been a challenging problem for years. This paper describes a new block-matching algorithm that is much faster than the full search algorithm and occasionally even produces better rate-distortion curves than the full search algorithms. We observe that a piecewise continuous motion field reduces the bit rate for differentially encoded motion vectors. Our motion estimation algorithm exploits the spatial correlations of motion vectors effectively in the sense of producing better rate-distortion curves. Furthermore, we incorporate such correlations in a multiresolution framework to reduce the computational complexity. Simulation shows that this method is successful because of the homogeneous and reliable estimation of the displacement vectors. In nine out of our ten benchmark simulations, the performance of the full search algorithm and that of our subblock multiresolution method is about the same. In one out of our ten benchmark simulations, our method has improvement.
RAR  316
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Sung Ho Cho, Rin Chul Kim, Seung Seok Oh, and Sang Uk Lee A Coding Technique for the Contours in Smoothly Perfect Eight-Connectivity Based on Two-Stage Motion Compensation
AbstractIn this paper, a new contour-coding technique for object-oriented video coding is proposed. In our approach, the two-stage motion compensation technique is considered, in order to cope with the rather complex motion of the object. While the object-based motion compensation is performed in the first stage, the second-stage motion compensation is carried out to search the best match of the contours, which are not motion compensated in the first stage. Also, by introducing the notion of the error band, the current contours can be properly fitted to the motioncompensated contours using the interframe relationship of the contours. In addition, an efficient technique for encoding the contours, simplified by the majority filter, is also proposed. From the simulation result, it is shown that the proposed technique provides better performance than the content-based arithmetic encoding, especially when lossy encoding is allowed. Moreover, by varying the width N of the error band, it is shown that the bit amount for the shape information can be adjusted according to the channel condition.
RAR  774
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Zhaohui Sun and A. Murat Tekalp Trifocal Motion Modeling for Object-Based Video Compression and Manipulation
AbstractFollowing a brief overview of two-dimensional (2-D) parametric motion models commonly used in video manipulation and compression, we introduce trifocal transfer, which is an image-based scene representation used in computer vision, as a motion compensation method that uses three frames at a time to implicitly capture camera/scene motion and scene depth. Trifocal transfer requires a trifocal tensor that is computed by matching image features across three views and a dense correspondence between two of the three views. We propose approximating the dense correspondence between two of the three views by a parametric model in order to apply the trifocal transfer for object-based video compression and background mosaic generation. Backward, forward, and bidirectional motion compensation methods based on trifocal transfer are presented. The performance of the proposed motion compensation approaches using the trifocal model has been compared with various other compensation methods, such as dense motion, block motion, and global affine transform on several video sequences. Finally, video compression and mosaic synthesis based on the trifocal motion model are implemented within the MPEG-4 Video Verification Model (VM), and the results are compared with those of the standard MPEG-4 video VM. Experimental results show that the trifocal motion model is superior to block and affine models when there is depth variation and camera translation.
RAR  694
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Pei-Chuan Liu and Wen-Thong Chang Recursive Wiener Filter for Motion Parameter Estimation in Three-Parameter Motion Model
AbstractMotion compensation is used to reduce the displaced frame difference (DFD) during the video coding. To increase the accuracy of the point correspondence during the compensation, a three-parameter motion model is considered. The matching error can be significantly reduced as compared with that of the twoparameter block matching. To derive the parameters, a partial full search method is used. The full search is used when the zoom value is set at one. Otherwise, the gradient-based algorithm is used. Since the DFD is a nonlinear function of the image gradients and the motion parameters, a linearized model is considered. To eliminate the linearization error, Wiener filtering is used to smoothen the DFD to improve the convergence condition of the iterative gradient search. To make the gradient-based search more robust to the gradient variation, several gradient estimation methods are also compared.
RAR  508
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Michael C. Chen, and Alan N. Willson, Jr., Fellow Rate-Distortion Optimal Motion Estimation Algorithms for Motion-Compensated Transform Video Coding
AbstractMotion estimation and compensation is widely used for exploiting temporal correlation within an image sequence. To find motion vectors that lead to high compression, most motion estimation approaches use a source distortion measure, such as mean-square error (MSE) or mean-absolute error (MAE), as a search criterion. When incorporated into a closed-loop motioncompensated (MC) transform video coder, these schemes produce noisy motion fields which significantly increase the bit-rates required to represent motion vectors. In view of this problem, this paper presents a rate-distortion optimal motion estimation algorithm. The proposed scheme improves rate performance of the estimated motion field while maintaining the peak signalto- noise ratio (PSNR) prediction quality of the distortion-based methods, thereby enabling an efficient bit allocation between motion information and transform-coded prediction residuals. For coders in which motion vectors are differentially encoded, the rate-distortion optimization process is formulated as a shortestpath- finding problem. Adopting this framework, we show that the optimal solution for the conventional block-based motion estimation, followed by one-dimensional (1-D) differential coding and Huffman coding, can be obtained by using dynamic programming or the Viterbi algorithm. Since memory and computational requirements for the optimal algorithm increase dramatically with the search range, we propose an effective fast algorithm that closely approximates the optimal performance while requiring considerably less complexity. When used in a hybrid MC coding system, the proposed scheme outperforms the conventional MSEor MAE-optimal motion estimation approach in terms of PSNR performance under a low-bit-rate constraint. Our experimental results demonstrate overall gains in the range of 0.31.5 dB.
RAR  863
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Seongsoo Lee, Jeong-Min Kim, and Soo-Ik Chae New Motion Estimation Algorithm Using Adaptively Quantized Low Bit-Resolution Image and Its VLSI Architecture for MPEG2 Video Encoding
AbstractThis paper describes a new motion estimation algorithm that is suitable for hardware implementation and substantially reduces the hardware cost by using a low bit-resolution image in the block matching. In the low bit-resolution image generation, adaptive quantization is employed to reduce the bit resolution of the pixel values, which is better than simple truncation of the least significant bits in preserving the dynamic range of the pixel values. The proposed algorithm consists of two search steps: in the low-resolution search, a set of candidate motion vectors is determined, and in the full-resolution search, the motion vector is found from these candidate motion vectors.
RAR  299
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Rajesh Rajagopalan, Ephraim Feig, and Michael T. Orchard Motion Optimization of Ordered Blocks for Overlapped Block Motion Compensation
Abstract While overlapped block motion compensation (OBMC) [1][3] with block matching motion vectors yields better estimation accuracy than standard block matching, these estimates may be significantly improved by optimizing the motion vectors. Optimal motion vectors may be determined by an iterative and computationally intensive process. However, for a low-cost system (e.g., videoconferencing [4]), such an approach is not feasible. An analysis of the compensation errors after motion optimization reveals that most gains in estimation accuracy result from the optimization of a fraction of the total number of blocks in a frame. It is thus conceivable that, by defining suitable ordering algorithms for blocks, coding systems could see improved performance by optimizing some number of blocks based on the ordering depending on available computational resources. In this paper, with the aid of simulations we first show that most improvements by optimizing motion are limited to a few motion vectors. Then we present simple and intuitive algorithms based on compensation error after OBMC with block matching vectors to order blocks. Simulation results using these algorithms for ordering and optimizing motion are presented for two video sequences. The results reveal improvements obtained by optimizing motion of blocks from the ordering are reasonable; however, the improvements are not limited to the first fraction of blocks from the ordering, suggesting that better ordering algorithms be investigated in the future.
RAR  94
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Dimitrios Tzovaras and Michael G. Strintzis Motion and Disparity Field Estimation Using Rate-Distortion Optimization
Abstract A rate-distortion framework is used to define a displacement vector field estimation technique for use in video coding. This technique achieves maximum reconstructed image quality under the constraint of a target bit rate for the coding of the vector sequence. The technique may be adapted so as to limit its smoothing effect to homogeneous areas and avoid highly textured areas and edges. Use of this technique is evaluated for two application areas in which the need for high compression of displacement vector fields is particularly acute. The first is motion field coding for very-low-bit-rate image sequence transmission, as in video-phone applications. The second application area is coding for the transmission of dense disparity fields. This is needed for the generation at the receiver of intermediate viewpoints through spatial interpolation. It is also needed in a number of other applications requiring accurate depth knowledge, including three-dimensional medical data transmission and transmission of scenes to be postprocessed using depth-keyed segmentation. Experimental results illustrating the performance of the proposed technique in these application areas are presented and evaluated.
RAR  295
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Ut-Va Koc, and K. J. Ray Liu Interpolation-Free Subpixel Motion Estimation Techniques in DCT Domain
AbstractCurrently existing subpixel motion estimation algorithms require interpolation of interpixel values which undesirably increases the overall complexity and data flow and deteriorates estimation accuracy. In this paper, we develop discrete cosine transform (DCT)-based techniques to estimate subpel motion at different desired subpel levels of accuracy in the DCT domain without interpolation. We show that subpixel motion information is preserved in the DCT of a shifted signal under some condition in the form of pseudophases, and we establish subpel sinusoidal orthogonal principles to extract this information. The proposed subpixel techniques are flexible and scalable in terms of estimation accuracy with very low computational complexity O(N2) compared to O(N4) for the full-search block-matching approach and its subpixel versions. Above all, motion estimation in the DCT domain instead of the spatial domain simplifies the conventional hybrid DCT-based video coder, especially the heavily loaded feedback loop in the conventional design, resulting in a fully DCT-based high-throughput video codec. In addition, the computation of pseudophases is local, and thus a highly parallel architecture is feasible for the DCT-based algorithms. Finally, simulation on video sequences of different characteristics shows comparable performance of the proposed algorithms to block-matching approaches.
RAR  1270
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Seongman Kim, Seunghyeon Rhee, Jun Geun Jeon, and Kyu Tae Park Interframe Coding Using Two-Stage Variable Block-Size Multiresolution Motion Estimation and Wavelet Decomposition
Abstract In this paper, we propose a two-stage variable block-size multiresolution motion estimation (MRME) algorithm. In this algorithm, a method to reduce the amount of motion information is developed, and a bit allocation method minimizing the sum of the motion information and the prediction error is obtained in the wavelet transform domain. In the first stage of the proposed scheme, we utilize a set of wavelet components of the four subbands in the lowest resolution. These motion vectors are directly used as motion vectors for the lowest subband, and are scaled into the initial biases for other subbands at every layer of the wavelet pyramid. In the second stage, the bottom-up construction of a quadtree based on the merge operation is performed. The proposed scheme reduces the uncompressed bit rate of 8 bits/pixel into 0.212 bits/pixel at 41.1 dB of PSNR for the Claire sequence, which can be regarded as nearly an 11% decrease compared with the conventional method.
RAR  378
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Soo-Chang Pei, Ching-Wen Ko, and Ming-Shing Su Global Motion Estimation in Model-Based Image Coding by Tracking Three-Dimensional Contour Feature Points
AbstractRecently a new type of video coding method called model-based image coding has attracted much attention as a potential candidate for low bit-rate visual communication services. This technique reconstructs the facial image with a preknown three-dimensional (3-D) human face model and its received model motion parameters. The parameters of the head motion are mainly divided into two parts: global motion parameters describe the rigid movement of the head, such as rotation and translation, and local motion parameters which deal with the nonrigid movements of facial expressions, such as the opening and closing of the mouth and eyes. In this paper, we propose a new approach which can estimate the head global motion more robustly and accurately. Comparing with the existing techniques to match only a few key points, here we extract 3-D contour feature points and use chamfer distance matching to estimate head global motion. This can improve and enhance the contour tracking performance greatly. We also develop another technique called facial normalization transform. It maps the facial region of the current input frame back to the normalized pose of the initial frame. Using this transform, we can analyze facial expressions at the same orientation and fixed region. This simplifies the analysis work a lot. Then, we do our encoding by the clip-and-paste method along with adaptive codebook technique. In the following, the coder and decoder system are briefly described. Since we mainly focus the work on the analysis and synthesis of the facial portion images, background analysis and bitstream coding technique will not be discussed in this paper.
RAR  310
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Tien-ying Kuo and C.-C. Jay Kuo Fast Overlapped Block Motion Compensation with Checkerboard Block Partitioning
AbstractThe overlapped block motion compensation (OBMC) scheme provides an effective way to reduce blocking artifacts in video coding. However, in comparison with the traditional block motion compensation (BMC), its complexity of motion estimation increases significantly due to the interdependency of motion vectors. In this work, a new fast motion estimation algorithm is proposed for OBMC based on the checkerboard block partitioning and grouping in encoding. This algorithm, called the grouped OBMC (GOBMC), effectively decorrelates dependency among OBMC motion vectors and facilitates the search process. In comparison with traditional iterative OBMC motion search, GOBMC performs motion estimation only once per macroblock at the encoder, and reaches a local optimal solution with degradation of 0.050.1 dB. At the decoding end, we also propose a fast OBMC reconstruction scheme which reduces the complexity of multiplication to 38% of that of traditional OBMC reconstruction while preserving the same visual quality as obtained via BMC search with OBMC reconstruction.
RAR  262
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Dzung T. Hoang, Philip M. Long, and Jeffrey Scott Vitter, Fellow Efficient Cost Measures for Motion Estimation at Low Bit Rates
Abstract We present and compare methods for choosing motion vectors for block-based motion-compensated video coding. The primary focus is on videophone and videoconferencing applications, where low bit rates are necessary, where motion is usually limited, and where the amount of computation is also limited. In a typical block-based motion-compensated video coding system, motion vectors are transmitted along with a lossy encoding of the residuals. As the bit rate decreases, the proportion required to transmit the motion vectors increases. We provide experimental evidence that choosing motion vectors explicitly to minimize rate (including motion vector coding), subject to implicit constraints on distortion, yields better ratedistortion tradeoffs than minimizing some measure of prediction error.
RAR  474
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Showbhik Kalra, and Man-Nang Chong Bidirectional Motion Estimation via Vector Propagation
AbstractA low-complexity vector propagation (VP) algorithm is introduced for the estimation of bidirectional motion vector fields in image sequences. The proposed VP algorithm exploits the strong correlation between forward and backward motion vector fields in image sequences. The performance of the VP algorithm is compared to that of a bidirectional multiresolution blockmatching (MRBM) motion estimation (ME) algorithm. Computer simulation results demonstrate that with the VP algorithm, the computational workload of the bidirectional ME is reduced by a factor of nearly 2. The robustness of the VP algorithm is extensively tested using computer generated image sequences and real movies for a motion picture restoration (MPR) system. It is shown that the VP algorithm is robust enough to be used in the computationally demanding MPR algorithm, in which the performance of the novel VP algorithm is close to that of a bidirectional MRBM ME algorithm. With this technique, other video processing systems that desire to take advantage of bidirectional motion estimation can now do so without an excessive increase in computing time.
RAR  876
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Thomas Meier and King N. Ngan Automatic Segmentation of Moving Objects for Video Object Plane Generation
AbstractThe new video coding standard MPEG-4 is enabling content-based functionalities. It takes advantage of a prior decomposition of sequences into video object planes (VOPs) so that each VOP represents one moving object. A comprehensive review summarizes some of the most important motion segmentation and VOP generation techniques that have been proposed. Then, a new automatic video sequence segmentation algorithm that extracts moving objects is presented. The core of this algorithm is an object tracker that matches a two-dimensional (2-D) binary model of the object against subsequent frames using the Hausdorff distance. The best match found indicates the translation the object has undergone, and the model is updated every frame to accommodate for rotation and changes in shape. The initial model is derived automatically, and a new model update method based on the concept of moving connected components allows for comparatively large changes in shape. The proposed algorithm is improved by a filtering technique that removes stationary background. Finally, the binary model sequence guides the extraction of the VOPs from the sequence. Experimental results demonstrate the performance of our algorithm.
RAR  264
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Dae-Sung Cho and Rae-Hong Park An Object-Oriented Coder Using Block-Based Motion Vectors and Residual Image Compensation
Abstract This paper proposes a two-stage global motion parameter estimation method using block-based motion vectors and a model failure (MF) object compensation algorithm by object-oriented fractal mapping of the residual image for an object-oriented coder. In the first stage of the two-stage motion parameter estimation algorithm, coarse motion parameters are estimated by fitting block-based motion vectors computed hierarchically to a six-parameter model, and in the second stage, the estimated motion parameters are refined by the gradient method using an image reconstructed by motion parameters detected in the first stage. The local prediction error by the six-parameter method is locally reduced by blockwise motion parameter correction using the residual image. Finally, the MF object is compensated by object-oriented fractal mapping of the previous residual image into the current one, in which geometric affine mapping is followed by the massic transformation. For MF object compensation, selection between motion parameter compensation and fractal mapping is achieved by the validity test.
RAR  391
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Gerard de Haan, and Paul W. A. C. Biezen An Efficient True-Motion Estimator Using Candidate Vectors from a Parametric Motion Model
AbstractSome efficient motion estimation algorithms select their output motion vector from a limited number of likely correct candidate, or prediction, vectors. In this paper, next to the known spatial and temporal prediction vectors, an additional and independent prediction is proposed. This candidate is generated with a parametric model describing the global motion in a previously estimated motion vector field. The proposal is elaborated as an addition to the three-dimensional (3-D) recursive search block-matching algorithm. The evaluation shows that a subpixel accurate, true-motion estimator results with a very low operations count.
RAR  236
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Jo Yew Tham, Surendra Ranganath, Maitreya Ranganath, and Ashraf Ali Kassim A Novel Unrestricted Center-Biased Diamond Search Algorithm for Block Motion Estimation
AbstractThe widespread use of block-based interframe motion estimation for video sequence compression in both MPEG and H.263 standards is due to its effectiveness and simplicity of implementation. Nevertheless, the high computational complexity of the full-search algorithm has motivated a host of suboptimal but faster search strategies. A popular example is the three-step search (TSS) algorithm. However, its uniformly spaced search pattern is not well matched to most real-world video sequences in which the motion vector distribution is nonuniformly biased toward the zero vector. Such an observation inspired the new three-step search (NTSS) which has a center-biased search pattern and supports a halfway-stop technique. It is faster on the average, and gives better motion estimation as compared to the well-known TSS. Later, the four-step search (4SS) algorithm was introduced to reduce the average case from 21 to 19 search points, while maintaining a performance similar to NTSS in terms of motion compensation errors. In this paper, we propose a novel unrestricted center-biased diamond search (UCBDS) algorithm which is more efficient, effective, and robust than the previous techniques. It has a best case scenario of only 13 search points and an average of 15.5 block matches. This makes UCBDS consistently faster than the other suboptimal block-matching techniques. This paper also compares the above methods in which both the processing speed and the accuracy of motion compensation are tested over a wide range of test video sequences.
RAR  262
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K. J. Boo and N. K. Bose, Fellow A Motion-Compensated Spatio-Temporal Filter for Image Sequences with Signal-Dependent Noise
AbstractIn this paper, a novel spatio-temporal filter is described for monochrome image sequences with either signalindependent or signal-dependent noise by considering both spatial and temporal correlations. With the assumptions of spatiotemporal separability and temporal stationarity, it is shown that motion-compensated groups of frames can be decorrelated by using the KarhunenLoeve transform. Practical filters that work well on a variety of image sequences are developed by first applying the Hadamard transform along the temporal direction. Subsequently, the parametric adaptive Wiener filter is applied to each of the resulting approximately decorrelated transformed images. These transformed images are classified into one average image and a remaining set of residual images, which provide interesting and useful interpretations of the type of image sequence. The filter performance is evaluated by considering different types of image sequences in the database. The procedure advanced for processing a sequence of monochrome images can be adapted for generalization to multispectral images and this possibility is currently under detailed investigation.
RAR  511
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Hangu Yeo, and Yu Hen Hu Modular High-Throughput Architecture for Logarithmic Search Block-Matching Motion Estimation
Abstract In this paper, a high-throughput modular architecture for a logarithmic search block-matching algorithm is presented. The design efforts are focused on exploiting the search area data dependencies using special data input ordering constraints. The input bandwidth problem has been solved by a random access on-chip memory, and a simple address generation procedure has been described. Furthermore, this architecture can handle a large search range with unequal horizontal and vertical spans using a technique called pipeline interleaving. Compared to the existing architectures for the three-step search BMA, this architecture delivers a high throughput rate with fewer input lines, and is linearly scalable.
RAR  845
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Viet L. Do and Kenneth Y. Yun A Low-Power VLSI Architecture for Full-Search Block-Matching Motion Estimation

RAR  242
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Steve Calzone, Keshi Chen, Chih-Chwen Chuang, Ajay Divakaran, Simant Dube, Lyman Hurd, Jarkko Kari, Gang Liang, Fu-Huei Lin, John Muller, and Hawley K. Rising, III Video Compression by Mean-Corrected Motion Compensation of Partial Quadtrees
AbstractThis paper presents an architectural enhancement to reduce the power consumption of the full-search block-matching (FSBM) motion estimation. Our approach is based on eliminating unnecessary computation using conservative approximation. Augmenting the estimation technique to a conventional systolicarchitecture- based VLSI motion estimation reduces the power consumption by a factor of 2, while still preserving the optimal solution and the throughput. A register-transfer level implementation as well as simulation results on benchmark video clips are presented.
RAR  493
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Hirohisa Jozawa, Kazuto Kamikura, Atsushi Sagata, Hiroshi Kotera, and Hiroshi Watanabe Two-Stage Motion Compensation Using Adaptive Global MC and Local Affine MC
AbstractThis paper describes a high-efficiency video coding method based on ITU-T H.263. To improve the coding efficiency of H.263, a two-stage motion compensation (MC) method is proposed, consisting of global MC (GMC) for predicting camera motion and local MC (LMC) for macroblock prediction. First, global motion such as panning, tilting, and zooming is estimated, and the global-motion-compensated image is produced for use as a reference in LMC. Next, LMC is performed both for the global-motion-compensated reference image and for the image without GMC. LMC employs an affine motion model in the context of H.263s overlapped block motion compensation. Using the overlapped block affine MC, rotation and scaling of small objects can be predicted, in addition to translational motion. In the proposed method, GMC is adaptively turned on/off for each macroblock since GMC cannot be used for prediction in all regions in a frame. In addition, either an affine or a translational motion model is adaptively selected in LMC for each macroblock. Simulation results show that the proposed video coding technique using the two-stage MC significantly outperforms H.263 under identical conditions, especially for sequences with fast camera motion. The performance improvements in peak-to-peak SNR (PSNR) are about 3 dB over the original H.263, which does not use the two-stage MC.
RAR  763
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Demin Wang, Claude Labit, and Joseph Ronsin Segmentation-Based Motion-Compensated Video Coding Using Morphological Filters
AbstractThe number of regions and length of contour are two basic constraints in segmentation-based motion-compensated video coding. This paper presents a coding scheme which focuses on region number reduction, contour coding, and displaced frame difference (DFD) compression. One of the important features of the proposed scheme is a spatiotemporal simplification algorithm based on morphological filters, with which an image can be segmented into a small number of regions. Another important feature of the scheme is a segmentation map sampling technique which reduces contour length by about 50% with a very small reconstruction error. Experimental results show that, using the proposed scheme, a high compression ratio can be achieved with a small coding error for video sequences such as Miss America and Foreman.
RAR  213
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Dimitrios Tzovaras, Nikos Grammalidis, and Michael G. Strintzis Object-Based Coding of Stereo Image Sequences Using Joint 3-D Motion/Disparity Compensation
AbstractAn object-based coding scheme is proposed for the coding of a stereoscopic image sequence using motion and disparity information. A hierarchical block-based motion estimation approach is used for initialization, while disparity estimation is performed using a pixel-based hierarchical dynamic programming algorithm. A split-and-merge segmentation procedure based on three-dimensional (3-D) motion modeling is then used to determine regions with similar motion parameters. The segmentation part of the algorithm is interleaved with the estimation part in order to optimize the coding performance of the procedure. Furthermore, a technique is examined for propagating the segmentation information with time. A 3-D motion-compensated prediction technique is used for both intensity and depth image sequence coding. Error images and depth maps are encoded using discrete cosine transform (DCT) and Huffman methods. Alternately, an efficient wireframe depth modeling technique may be used to convey depth information to the receiver. Motion and wireframe model parameters are then quantized and transmitted to the decoder along with the segmentation information. As a straightforward application, the use of the depth map information for the generation of intermediate views at the receiver is also discussed. The performance of the proposed compression methods is evaluated experimentally and is compared to other stereoscopic image sequence coding schemes.
RAR  1245
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Junavit Chalidabhongse, and C.-C. Jay Kuo Fast Motion Vector Estimation Using Multiresolution-Spatio-Temporal Correlations
AbstractIn this paper, we propose a new fast algorithm for block motion vector (MV) estimation based on the correlations of the MVs existing in spatially and temporally adjacent as well as hierarchically related blocks.We first establish a basic framework by introducing new algorithms based on spatial correlation and then spatio-temporal correlations before integrating them with a multiresolution scheme for the ultimate algorithm. The main idea is to effectively exploit the information obtained from the corresponding block at a coarser resolution level and spatiotemporal neighboring blocks at the same level in order to select a good set of initial MV candidates and then perform further local search to refine the MV result. We show with experimental results that, in comparison with the full search algorithm, the proposed algorithm achieves a speed-up factor ranging from 150 to 310 with only 27% mean square error (MSE) increase and a similar rate-distortion performance when applied to typical test video sequences.
RAR  328
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Mei-Juan Chen, Liang-Gee Chen, and Ro-Min Weng Error Concealment of Lost Motion Vectors with Overlapped Motion Compensation
AbstractA new error concealment algorithm for recovering the lost or erroneously received motion vectors is presented. It combines the overlapped motion compensation and the side match criterion to make the effect of lost motion vectors subjectively imperceptible. The side match criterion takes advantage of the spatial contiguity and interpixel correlation of image to select the best-fit replacement among the motion vectors of spatially contiguous candidate blocks. Particularly, to mask the blocking artifacts, we incorporate an overlapping technique to create a subjectively closer approximation to the true error-free image.
RAR  121
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Edouard Francois, Jean-Francois Vial, and Bertrand Chupeau Coding Algorithm with Region-Based Motion Compensation
Abstract This paper describes a region-based coding algorithm developed by Thomson Multimedia and submitted to MPEG-4 tests of November 1995 and January 1996. In this algorithm, the segmentation into regions is based on an advanced motion analysis, successively achieving a multiresolution motion field estimation and a segmentation based on a Markovian statistical approach, which insures a good temporal coherence of segmentation maps and an identification of covered areas. Moreover, the accurate motion description allows an intermediate frames interpolation which can increase the displayed frame rate. Simulation results and MPEG-4 tests of January 1996 have shown that the algorithm is as efficient as block-based coding algorithms like MPEG-1 or H.263 for the compression functionality, while offering temporal scalability by higher frame rates. Moreover, description of the scene in coherent motion regions may be seen as an intermediate step toward object-based functionalities.
RAR  311
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Weiping Li, Hugh Q. Cao, Shipeng Li, Fan Ling, Scott A. Segan, Hongqiao Sun, John P. Wus, and Ya-Qin Zhang A Video Coding Algorithm Using Vector-Based Techniques
AbstractThis paper presents an algorithm proposal submitted to MPEG-4 for video coding. The proposed algorithm addresses the functionality of improved coding efficiency for compression. It uses vector-based techniques for coding intraframes (the first frame and subsequent refreshing key frames) and motion-compensated difference frames. It uses the same motion estimation and motion compensation techniques as H.263. A video frame (I or P frame) is first decomposed into a set of vector bands using a vector wavelet transform. This stage of vectorbased signal processing makes subsequent vector quantization in the vector bands very efficient. Lattice vector quantization is then used in the vector bands. A 100% labeling efficiency is achieved for lattice vector quantization by using a set of generalized labeling algorithms for various important lattices with pyramid and sphere boundaries. Finally, entropy coding is used to code the indexes generated from lattice vector quantization. Our coding results have shown that a gain in peak signal-to-noise ratio (PSNR) up to 8 dB for intraframe coding and up to 6 dB for interframe coding can be achieved over H.263. Subjective quality improvement of the proposed algorithm over H.263 can be easily observed.
RAR  789
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Ming-Chieh Lee, Wei-ge Chen, Chih-lung Bruce Lin, Chuang Gu, Tomislav Markoc, Steven I. Zabinsky, and Richard Szeliski A Layered Video Object Coding System Using Sprite and Affine Motion Model
AbstractA layered video object coding system is presented in this paper. The goal is to improve video coding efficiency by exploiting the layering of video and to support content-based functionality. These two objectives are accomplished using a sprite technique and an affine motion model on a per-object basis. Several novel algorithms have been developed for mask processing and coding, trajectory coding, sprite accretion and coding, locally affine motion compensation, error signal suppression, and image padding. Compared with conventional frame-based coding methods, better experimental results on both hybrid and natural scenes have been obtained using our coding scheme. We also demonstrate content-based functionality which can be easily achieved in our system.
RAR  879
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G.de Haan and H.Huijen Motion Estimator For TV-picture Enhacement
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RAR  618
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Gerard de Haan, Paul W.A.C. Biezen, Henk Huijgen, and Olukayode A. Ojo Graceful Degradation in Motion-Compensated Field-Rate Conversion
Recent motion estimation algorithms have reached a quality level that allows an improved motion portrayal for field rate conversion systems. As, in practice, still situations may occur in which motion estimation fails, a strategy for graceful degradation is required, to prevent the possible artifacts resulting from the processing from outweighing its advantages. In this paper both a global fall back detection and processing mode is introduced, and a novel method applying ordered statistical filtering in the up-convertor that realizes a graceful degradation for local errors in the estimated motion vector field.
RAR  218
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B. De Loore, P. Lippens, P. Eeckhout, H. Huijgen, A. Loning, B. McSweeney, M. Verstraelen, B. Pham, G. de Haan, J. Kettenis A video signal processor for motioncompensated field-rate upconversion in consumer television
The four embedded video signal processors on this IC provide a processing power of 10 Gops. Their architecture was generated from an algorithm description using behavioural synthesis. The required 25 Gbit/s memory bandwidth was realized by embedding 24 single/dual port SRAM/DRAM instances. The test approach includes full scan, boundary scan, functional, built-in-self-test and IDDq-test.
RAR  80
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D. Bagni, G. de Haan, V. Riva MOTION COMPENSATED POST-PROCESSING FOR LOW BIT RATE VIDEOCONFERENCING ON ISDN LINES
This paper presents a post-processing algorithm for low bit rate videoconferencing on ISDN lines. The relatively few images per second that are transmitted during low bit rate multi-media communications are up-converted after decoding inside the terminal receiver to an increased frame rate of 25 Hz or 30 Hz, depending on the display. Applying advanced motion estimation and compensation techniques can achieve a significant improvement in motion portrayal of moving objects.
RAR  75
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Olukayode Anthony Ojo and Gerard de Haan Robust motion-compensated video upconversion
Abstract: The quality of eld-rate conversion improves signi cantly with motion-compensation techniques. It becomes possible to interpolate new elds at their correct temporal position. This re- sults in smooth motion portrayal without loss of temporal resolution. However, motion vectors are not always valid for every pixel or object in an image. Therefore, visible artifacts occur wherever such wrong vectors are used on the image. One e ective method to solve this problem is the use of non-linear ltering. In this method, a wrongly interpolated pixel is either substituted or averaged with neighbouring pixels. In this paper we introduce and evaluate a new and very robust upconversion algorithm which is based on the non-linear ltering ap- proach. It is unique in that it estimates mo- tion vector reliability and uses this information to control the ltering process. This algorithm outperforms others in its class, especially when we have complex image sequences.
RAR  3631
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E.B. Bellers and G. de Haan New Algorithm for Motion Estimation on Interlaced Video
Many video processing algorithms can pro t from motion information. Therefore, motion estimation is often an integral part of advanced video processings algorithms. This paper focuses on the estimation of true-motion vectors, that are required for scan-rate-conversion. Two recent motion estimator methods will be discussed. By combining these two methods, the major drawbacks of the individual MEs is eliminated. The new resulting motion estimator proves to be superior over alternatives in an evaluation.
RAR  505
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R.J. Schutten, A. Pelagotti and G. de Haan Layered motion estimation
Abstract:{ A layered motion estimation algorithm is proposed that permits quasi-simultaneous motion estimation / segmentation up to a xed maximum number of layers. The estimation results in one motion parameter set per layer, and a segmentation map that assigns these sets to di erent parts of the image (motion layers). Motion in a layer is modelled with at maximum four parameters capable of describing pan, tilt and zoom. The concept shows some hierarchy, i.e. a ranking of the motion layers. In this way the motion parameter estimation concerning one layer is excluding those parts of the image that have been described by a layer ranked higher in the hierarchy and are not polluted by parts of the image that are better described by layers ranked lower in the hierarchy. The concept results in a very low operations count. It has been shown to perform well even in critical scan rate conversion applications, particularly in picture rate up-conversion. A variant including three layers has been scheduled to run in real-time on a Philips TriMedia processor.
RAR  472
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E.B. Bellers and G. de Haan Analysis of sub-pixel Motion Estimation
The use of interpolation lters in a motion estimator to realize sub-pixel shifts, may lead to unintentional preferences for some velocities over other. In this paper we analize this phenomenon, focussing on the case of interlaced image data where the problem leads to the most pronounced errors. Linear interpolators, either applied directly or indirectly using generalized sampling are discussed. The conclusions are applicable to any type of motion estimator.
RAR  428
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Gerard de Haan IC FOR MOTION-COMPENSATED DE-INTERLACING, NOISE REDUCTION, AND PICTURE-RATE CONVERSION
An IC1 for consumer television applies motion estimation and compensation for high quality video format conversion. The chip achieves perfect motion portrayal for all sources including 24, 25, and 30 Hz film material, and many display formats. The true-motion vectors are estimated with a sub-pixel resolution and are used to optimally de-interlace video broadcast signals, perform a motion compensated picture rate conversion and improve temporal noise reduction.
RAR  220
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Stefano Olivieriy, Gerard de Haan z, and Luigi Albaniy Noise{robust Recursive Motion Estimation for H.263{based videoconferencing systems
The key element in realizing low cost real{time software implementations of a H.263 video- conferencing system is a fast motion estimation algorithm, which only slightly decreases coding e.ciency. We propose a spatio{temporal recursive estimator that combines an excellent coding e.ciency with a high computational e.ciency. Experimentally, the new algorithm proves to be comparable to full{search block matching when encoding typical videoconferencing sequences in presence of additive noise, even though the computational burden has been greatly reduced.
RAR  138
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S. Olivieri, L. Albani ,G. de Haan A LOW{COMPLEXITY RECURSIVE MOTION ESTIMATION ALGORITHM FOR H.263 VIDEO CODING1
Abstract - The key element in realizing low cost real{time software implementations of a H.263 videoconferencing system is a fast motion estimation algorithm, which only slightly decreases coding e.ciency. We propose a spatio{temporal recursive estimator that combines an excel- lent coding e.ciency with a high computational e.ciency. Experiment- ally, the new algorithm proves to be comparable to full{search block matching when encoding typical videoconferencing sequences in pres- ence of additive noise, even though the computational burden has been greatly reduced.
RAR  484
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G. de Haan, Philips Research Laboratories, Eindhoven, The Netherlands PROGRESS IN MOTION ESTIMATION FOR CONSUMER VIDEO FORMAT CONVERSION
Two generations of application specific ICs for motion compensated consumer video format conversion (MCVFC) are available, and real time DSP software for MCVFC has recently been demonstrated. The breakthroughs enabling this progress have come from motion estimation. The paper gives an overview of the progress achieved in motion estimation for consumer electronics applications. to enhance the performance of block matchers. This improvement is discussed in Section 6, and later led to the first real-time software object-based motion estimator that is introduced in Section 7. We draw our conclusions in Section 8.
RAR  1034
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Mark J.W. Mertens ,Gerard de Haany A block-based motion estimator capable of handling occlusions
We present a new block-based motion estimation strategy, which aims at correctly nding the veloc- ity of picture blocks, even for background blocks in occlusion areas. This tritemporal ME calculates the motion between two pictures, switching the ME reference plane dependent on an occlusion detector. We also introduce a retimer, which can transform, locally in the picture, motion vectors valid for one time instant to another time instant. The retimer uses a foreground/background detector, of which we describe three varieties. Occlusion is a problem that plagues all block based motion estimation methods, and hence we see a utility of our method for ap- plications like e.g. picture rate conversion, video compression, 3D matching or image sequence object extraction. An evaluation of the tritemporal estima- tor is included.
RAR  277
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Rimmert Wittebrood and Gerard de Haan REAL-TIME RECURSIVE MOTION SEGMENTATION OF VIDEO DATA
Segmentation is a hot topic for video compression and interpolation. We introduce a recursive algorithm that enables real-time motion segmentation of standard definition video on a DSP. The evaluation of the separate optimization steps is included.
RAR  138
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Rimmert Wittebrood and Gerard de Haan REAL-TIME RECURSIVE MOTION SEGMENTATION OF VIDEO DATA ON A PROGRAMMABLE DEVICE
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RAR  706
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Rimmert Wittebrood and Gerard de Haan Feature point Selection for Object Based Motion Estimation on a Programmable Device
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Ralph Braspenningy, Gerard de Haany and Christian Hentschely Complexity Scalable Motion Estimation
Complexity scalable algorithms are capable of trading resource usage for output quality in a near-optimal way. We present a complexity scalable motion estimation algorithm based on the 3-D recursive search block matcher. We introduce data prioritizing as a new approach to scalability. With this approach, we achieve a near-constant complexity and a continuous quality-resource distribution. While maintaining acceptable quality, it is possible to vary the resource usage from below 1 match-error calculation per block on the average to more than 5 match-error calculations per block on the average.
RAR  291
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Ralph Braspenning and Gerard de Haan ficient Motion Estimation with Content-Adaptive Resolution
We present a motion estimation algorithm designed to fully exploit the flexibility offered by programmable platforms. This algorithm adapts its resolution to the image content using the highest spatial accuracy only for those parts of the image where it is required, i.e. near the borders of moving objects.
RAR  874
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Jie Wei and Ze-Nian Li An Enhancement to MRMC Scheme in Video Compression
AbstractZhang and Zafar proposed a video compression scheme based on the wavelet representation and multiresolution motion compensation (MRMC). In this letter, an additional masking module will be created to further enhance its efficiency. Specifically, between the modules of wavelet decomposition and MRMC, the masking module will be inserted which will construct binary images based on the difference of the wavelet coefficients. The binary images will serve as masks to facilitate a more efficient motion compensation. Experiments show that the processing time could be significantly reduced from what is required for a full search in the original MRMC algorithm. This section describes the original MRMC scheme [1] and the proposed enhanced MRMC. Without loss of generality, a wavelet decomposition pyramid of three levels will be used in this letter.
RAR  182
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Chun-Hung Lin and Ja-Ling Wu A Lightweight Genetic Block-Matching Algorithm for Video Coding
AbstractIn this paper, a lightweight genetic search algorithm (LGSA) is proposed. Different evolution schemes are investigated, such that the control overheads are largely reduced. It is also shown that the proposed LGSA can be viewed as a novel expansion of the three-step search algorithm (TSS). It can be seen from the simulation results that the performance of LGSA is very similar to that of FSA, and the computational complexity is much lower than that of FSA and other previously proposed genetic motion estimation algorithms.
RAR  174
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K. J. Boo and N. K. Bose, Fellow A Motion-Compensated Spatio-Temporal Filter for Image Sequences with Signal-Dependent Noise
AbstractIn this paper, a novel spatio-temporal filter is described for monochrome image sequences with either signalindependent or signal-dependent noise by considering both spatial and temporal correlations. With the assumptions of spatiotemporal separability and temporal stationarity, it is shown that motion-compensated groups of frames can be decorrelated by using the KarhunenLoeve transform. Practical filters that work well on a variety of image sequences are developed by first applying the Hadamard transform along the temporal direction. Subsequently, the parametric adaptive Wiener filter is applied to each of the resulting approximately decorrelated transformed images. These transformed images are classified into one average image and a remaining set of residual images, which provide interesting and useful interpretations of the type of image sequence. The filter performance is evaluated by considering different types of image sequences in the database. The procedure advanced for processing a sequence of monochrome images can be adapted for generalization to multispectral images and this possibility is currently under detailed investigation.
RAR  511
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Hao Bi and Wai-Yip Chan Rate-Distortion Optimization of Hierarchical Displacement Fields
AbstractThe displacement vector field for motion-compensated coding of image sequences is represented and coded using a hierarchy of displacement vector fields over successively finer sampling grids. An efficient method based on the generalized BreimanFriedmanOlshenStone (BFOS) tree-pruning algorithm is used to find a variable-depth hierarchy that satisfies a given bit rate or distortion constraint. The variable-depth hierarchy corresponds to using a nonuniformly sampled displacement field for motion compensation. The proposed scheme is compared with conventional fixed-block-size block-matching motion compensation. The motion information bit rate or the motioncompensation residual energy of the conventional scheme serves as the constraint. Simulation results show that the proposed scheme reduces the residual energy by between 0.61.5 dB, or the bit rate by 1954%, while using only 40100% of the computational complexity of the conventional scheme. The prediction image sequence produced by the hierarchical scheme offers much better viewing quality.
RAR  137
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Shanon X. Ju, Michael J. Black, Scott Minneman, and Don Kimber Summarization of Videotaped Presentations: Automatic Analysis of Motion and Gesture
AbstractThis paper presents an automatic system for analyzing and annotating video sequences of technical talks. Our method uses a robust motion estimation technique to detect key frames and segment the video sequence into subsequences containing a single overhead slide. The subsequences are stabilized to remove motion that occurs when the speaker adjusts their slides. Any changes remaining between frames in the stabilized sequences may be due to speaker gestures such as pointing or writing, and we use active contours to automatically track these potential gestures. Given the constrained domain, we define a simple set of actions that can be recognized based on the active contour shape and motion. The recognized actions provide an annotation of the sequence that can be used to access a condensed version of the talk from a Web page.
RAR  477
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Prakash Ishwar and Pierre Moulin On Spatial Adaptation of Motion-Field Smoothness in Video coding
AbstractMost motion-compensation methods dealt with in the literature make strong assumptions about the smoothness of the underlying motion field. For instance, block-matching algorithms assume a blockwise-constant motion field and are adequate for translational motion models; control-grid interpolation assumes a blockwise bilinear motion field and captures zooming and warping fairly well. Time-varying imagery, however, often contains both types of motion (as well as others), and hence exhibits a high degree of spatial variability of its motion-field smoothness properties. We develop a simple method to spatially adapt the smoothness of the motion field. The proposed method demonstrates substantial improvements in video quality over a wide range of bit rates. To this end, we introduce the notion of a motion field that is characterized by a set of labels. The labels provide the flexibility to adaptively switch between two different motion models locally. The individual motion models have very different smoothness properties. The switched framework for motion compensation performs significantly better than each of its constituent motion models, in terms of both visual quality and signal-to-noise ratio (0.30.7 dB on the average). Finally, we develop an extension of this method that enhances the overlapped block motion compensation scheme by allowing spatial adaptation of the window function.
RAR  598
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Yap-Peng Tan, Drew D. Saur, Sanjeev R. Kulkarni, and Peter J. Ramadge, Fellow Rapid Estimation of Camera Motion from Compressed Video with Application to Video Annotation
AbstractAs digital video becomes more pervasive, efficient ways of searching and annotating video according to content will be increasingly important. Such tasks arise, for example, in the management of digital video libraries for content-based retrieval and browsing. In this paper, we develop tools based on camera motion for analyzing and annotating a class of structured video using the low-level information available directly from MPEG-compressed video. In particular, we show that in certain structured settings, it is possible to obtain reliable estimates of camera motion by directly processing data easily obtained from the MPEG format. Working directly with the compressed video greatly reduces the processing time and enhances storage efficiency. As an illustration of this idea, we have developed a simple basketball annotation system which combines the low-level information extracted from an MPEG stream with the prior knowledge of basketball structure to provide high-level content analysis, annotation, and browsing for events such as wide-angle and close-up views, fast breaks, probable shots at the basket, etc. The methods used in this example should also be useful in the analysis of high-level content of structured video in other domains.
RAR  385
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